Japanese Unexamined Patent Application Publication No. HEI11(1999)-40310 discloses the technique by which plural electric wires is electrically and physically connected to the terminals by inserting the electric wire ends in the terminals and fusing them all at the same time. Such an electrified caulking device as used for an electrical conductor wire connecting device of a fusing type comprises a pair of electrodes for heating and pressurization which are made movable so as to be able to vary the distance between the two electrodes, a driving means to move at least one of the two, and a power source capable of feeding electricity to both the electrodes. When the above electrical conductor wire connecting device is used for its intended purpose, a cylinder-shaped terminal inserted with plural conductor wires each with insulating coating and held between both the electrodes is turned on electricity. The terminal, while kept in that state, is then pressurized by bringing both the electrodes closer to each other. Japanese Unexamined Patent Application Publication No. HEI11(1999)-40310 also describes that in the process of fusing the plural electric conductor wires in a lump, any excessive crush of the terminal (which may also be called as a “crimping connector” or “sleeve tube”) owing to temperature rise, hence the variability of crush of each electrical conductor wire, can be controlled by adjusting the positions of the two electrodes opposed to each other by a mechanical means as well as by reducing the current for electrification; with the result that it becomes possible to evenly pressurize each electrical conductor wire.
Further, Japanese Unexamined Patent Application Publication No. HEI11(1999)-40310 includes such descriptions that, when the crimping connector or sleeve tube is pinched for crushing with the electrodes each having a flat pressurizing surface in the conventional process of fusing the plural electric conductor wire ends in a lump, degree of crushing is less in the center part and both the end parts of the crimping connector, making it difficult to obtain even state of connection and causing different conditions of crushing to each and every electric conductor wire; and that in consideration of the foregoing events, proper adjustment should be made of the positions of the electrodes to be electrified, heated and pressurized and the strength of electrifying current so that force may be uniformly applied to each and every electric conductor wires in the crimping connector or sleeve tube.
Japanese Unexamined Patent Application Publication No. HEI5(1993)-38583 discloses a method for connecting plural coated conductor wires to connecting terminals, wherein plural coated conductor wire ends are twisted together and stored on plural hooks formed on the connecting terminals made of copper or copper alloy plate; the twisted wire ends are supported by plural hooks pressurized and deformed with electrode rods; and the electrode rods are electrified to remove coating from the coated conductor wires so as to electrically connect the wires to the hooks of the connecting terminals.
In the process of fusing many ends of wire all in a lump and when the electrode having a flat pressurizing surface is used to crush the crimping connector or sleeve tube, degree of crushing is less at both the end parts of the crimping connector than in the center part where the connector is pinched with the electrode. Therefore, in around the wire ends where the degree of crushing is little or less, it sometimes happens that the melted enamel coating cannot be squeezed out sufficiently, leaving the electrical connection in an incomplete state.
In the past, in the process of crushing the connector part of the electric conductor wire by means of a flat-surfaced electrode, the wire located at both the ends of the crushed connector part used to remain in an almost uncrushed state. To the contrary, the electric conductor wire located in the center part used to be crushed to a more-than-necessary degree, leading to the problem that a necessary cross-sectional area was hard to obtain. Furthermore, there is difference in the manner of being crushed between in the upper and lower parts of the connector part and in the center part of the connector; the crushing degree is high in the former and low in the latter.
As mentioned above, the crushing degree of the electrical conductor wire ends to be crushed within the connector part is different depending on where the wire ends are located in the connector part during the fusing process, but none of the crushing conditions was enough to crush all the connecting wire ends in a stable state. As a result, the enamel coating could not be squeezed out sufficiently from around the electrical conductor wire for which crushing was done only insufficiently, failing to complete electrical connection. On the contrary, the crushing degree is higher in the center part than in both the end parts, causing such problem that the electrical conductor wire became short in mechanical tensile strength.